Function UpdateNormalBetweenSegments

libs/drape_frontend/line_shape_helper.cpp:12–73

namespace
{
void UpdateNormalBetweenSegments(LineSegment * segment1, LineSegment * segment2)
{
  ASSERT(segment1 != nullptr && segment2 != nullptr, ());

  float const dotProduct = glsl::dot(segment1->m_leftNormals[EndPoint], segment2->m_leftNormals[StartPoint]);
  float const absDotProduct = fabs(dotProduct);
  float constexpr kEps = 1e-5;

  if (fabs(absDotProduct - 1.0f) < kEps)
  {
    // change nothing
    return;
  }

  float constexpr kMaxScalar = 5;
  float const crossProduct = glsl::cross(glsl::vec3(segment1->m_tangent, 0), glsl::vec3(segment2->m_tangent, 0)).z;
  if (crossProduct < 0)
  {
    segment1->m_hasLeftJoin[EndPoint] = true;
    segment2->m_hasLeftJoin[StartPoint] = true;

    // change right-side normals
    glsl::vec2 averageNormal =
        glsl::normalize(segment1->m_rightNormals[EndPoint] + segment2->m_rightNormals[StartPoint]);
    float const cosAngle = glsl::dot(segment1->m_tangent, averageNormal);
    float const widthScalar = 1.0f / sqrt(1.0f - cosAngle * cosAngle);
    if (widthScalar < kMaxScalar)
    {
      segment1->m_rightNormals[EndPoint] = averageNormal;
      segment2->m_rightNormals[StartPoint] = averageNormal;
      segment1->m_rightWidthScalar[EndPoint].x = widthScalar;
      segment1->m_rightWidthScalar[EndPoint].y = widthScalar * cosAngle;
      segment2->m_rightWidthScalar[StartPoint] = segment1->m_rightWidthScalar[EndPoint];
    }
    else
    {
      segment1->m_generateJoin = false;
    }
  }
  else
  {
    segment1->m_hasLeftJoin[EndPoint] = false;
    segment2->m_hasLeftJoin[StartPoint] = false;

    // change left-side normals
    glsl::vec2 averageNormal = glsl::normalize(segment1->m_leftNormals[EndPoint] + segment2->m_leftNormals[StartPoint]);
    float const cosAngle = glsl::dot(segment1->m_tangent, averageNormal);
    float const widthScalar = 1.0f / sqrt(1.0f - cosAngle * cosAngle);
    if (widthScalar < kMaxScalar)
    {
      segment1->m_leftNormals[EndPoint] = averageNormal;
      segment2->m_leftNormals[StartPoint] = averageNormal;
      segment1->m_leftWidthScalar[EndPoint].x = widthScalar;
      segment1->m_leftWidthScalar[EndPoint].y = widthScalar * cosAngle;
      segment2->m_leftWidthScalar[StartPoint] = segment1->m_leftWidthScalar[EndPoint];
    }
    else
    {